1. Field of Invention
The present invention relates to light pens and more particularly to a retraction mechanism of light pen with improved characteristics.
2. Related Art
A conventional PDA (personal digital assistant) 200 is shown in FIG. 1. A light pen 300 is adapted to touch an LCD (liquid crystal display) 400 in operation. Conventionally, a deep receptacle 210 is formed in the PDA 200 for receiving head of the light pen 300. Such arrangement is not desirable since the light pen 300 tends to disengage with the receptacle 210.
Another device having a prior ejection mechanism for a light pen is shown in FIG. 2. The mechanism is provided along one side of the device and comprises a deep receptacle for receiving a portion of the light pen, an elastic ejection device provided at bottom of the receptacle, the ejection device being adapted to be pressed by the head of the inserted light pen such that a further pressing of the light pen will release the stored elastic force of the ejection device to push the light pen out of the receptacle, an elastic locking device provided at one side proximate the bottom of the receptacle, a projecting member adapted to enter a groove proximate the head of the light pen, and a buffer member in the receptacle for engaging the light pen.
A further device having a prior fixing and ejection mechanism for a light pen is shown in FIG. 3. The mechanism is formed on a surface recess of the device and comprises a lower bag member and a pair of flexible upper arms extended therefrom. The head of a light pen is fastened by ends of the arms when the head of the light pen is inserted into the bag member.
However, the prior art suffered from a couple of disadvantages. For example, the ejection device may have an elastic fatigue problem after a relatively long period time of use. Further, the light pen may disengage with its receiving receptacle when a person touches the light pen unintentionally. Thus, the need for improvement still exists.